Combined fuse indicator and lock-in device



Jan. 26, 1943 w. c. LINTON 2,309,517

COMBINED FUSE INDICATOR AND LOCK-IN DEVICE :TEQE

Filed July 17, 1942 Patented Jan. 26, 1943 UNITED STATES PATENT OFFICE COllIBINED FUSE INDICATOR AND LOCK-IN DEVICE William C. Linton, Washington, D. 0., assignor to Fuse Indicator Corporation, Rockville, Md.

7 Claims.

This invention relates to mounting means for fuss blowout indicators, and particularly electrical indicators of that character designed for use in connection with ferrule, knife-blade and other conventional types of cartridge fuses, for the purpose of giving a visual signal or indication when the thermal element of the fuse is blown or ruptured. More particularly the invention relates to indicators and mounts therefor of the general type shown, for example, in my prior Patent No. 2,206,784, dated July 2, 19%, wherein the indicator comprises a casing detachably mounted upon a fuse by supporting brackets or legs forming conductors electrically connected with the usual fuse terminals, fuse holding clips and terminals of the electric circuit to be protected, such casing being supported in service above and parallel with the fuse and enclosing a signal device, such as a small neon lamp, which is energized or caused to glow and thereby give a signal or indication when the fuse is blown.

It is the general practice to mount the fuse holding clips in electrical connection with the circuit terminals by the use of fastening bolts conjointly securing the clips and circuit terminals to an insulating base or fuse box. In initially installing fuse and coacting indicator mounts for the use of a fuse and indicator of the character described, the same bolts have also been employed to secure the indicator holding brackets in position, brackets of suitable construction being provided for the purpose. If, however, fuse holding clips alone are initially mounted for the use of a fuse without an indicator, and it should be desired later to install bracket for the use Of an indicator, it may be found difficult or impossible to apply brackets designed to be held by the clip securing bolts. This is due to the fact that the nuts of the bolts, as well as the bolts, are often frozen or so firmly bound in position, due to rust or other causes, that it is impossible to remove the nuts, at least without possible damage to the installation or structure to which the installation is applied.

The fuse clips usually employed are U-shaped clips of spring metal. An objection to the use of such clips is that they often do not engage the fuse terminals with sufficient tightness to make a good electrical contact therewith, as a result of which arcing and undue heating at and in the region of the contact points takes place, causing annealing of the clips, blowing out of the fuse, charring of the fuse barrel, and other undesirable actions.

The primary object of my invention is to provide an indicator mounting means which overcomes the first-named objection, and by the use of which an indicator under the conditions mentioned may be securely mounted in position for cooperation with the fuse without disturbing the fastening bolts or nuts and without the necessity of utilizing them to fasten the indicator holding brackets in position.

Another object of my invention is to provide a novel construction of indicator holding brackets adapting them to be applied to the fuse clips so as to utilize such clips as the bracket supports, and which are designed to engage the clips in such manner as to be firmly and securely held in position and at the same time effect a tight clamping engagement between the clips and the fuse to prevent the undesirable actions above mentioned occurring under normal conditions of use when the clips do not fit the fuse contacts with sufficient tightness.

In the accompanying drawing illustrating certain exemplificative forms of my invention for carrying these objects into practical effect,

Figure 1 is a side elevation of a cartridge fuse and its holding clips and showing an indicator mounted for use therewith in accordance with my invention.

Figure 2 is an end elevation thereof.

Figure 3 is a vertical transverse section on the line 33 of Figure 1.

Figures 4, 5, 6 and 7 are, respectively, a side view, outer end elevational view, top plan View, and perspective view, of one of the indicator holding brackets or legs.

Figure 8 is an outer end elevational view of the other indicator holding bracket or leg.

Figure 9 is a horizontal transverse section taken substantialy on line 9-9 of Figure 3.

Figure 10 is a view of a fuse clip and indicator bracket showing by the indicating arrows the movements of the bracket jaws in bracket applying and removing operations.

Figure 11 is a view similar to Figure 3 showing the use of a modified form of indicator bracket.

Figure 12 is a perspective View of the modified form of indicator bracket per se.

Referring now more particularly to the drawing, I designates a cartridge type fuse consisting of a cylindrical body portion or barrel 2 provided at its opposite ends with the usual metal terminal caps, ferrules or other contact terminals 3 adapted for detachable engagement with the U- shaped fuse holding clips 4. These clips 4 may be of conventional type, each as shown being formed of spring metal and comprising a base 5 and bowed or curved clamping jaws 6, the jaws of the clips being adapted to receive and engage and clamp the fuse terminals between them. The base 5 is somewhat wider than the space between the jaws so that instruck, undercut or inwardly ofiset portions 1 are formed at the lower ends of the jaws and between the same and the base 5. The jaws as shown have their upper free ends 8 bent or turned outwardly to facilitate the downward insertion of the fuse from above into position. The clips 4 are secured with the electric circuit terminals 9 to an insulated base or fuse box ID by bolts ll, whose upper ends pas through the clip bases 5 and are fitted with securing nuts 12.

The indicator l3 employed to indicate the inoperative or blown condition of the fuse may be of the general type shown in the aforesaid Patent No. 2,206,784. This indicator comprises a cylindrical body or casing M in which is enclosed a miniature neon glow lamp having its leads connected with contact terminals l5 and H5 at the ends of the casing, one of which leads contains a leak resistance, which terminals are adapted for engagement with supporting brackets or legs I! and i8 electrically connecting the terminals with the fuse terminals 5 and the circuit terminals. The conducting connections are of such character as to connect the lamp in series with the contact terminals of the fuse, whose fusible element is also connected in series with said contact terminals but in parallel with the glow lamp, so that when the fusible element is blown or ruptured the current will pass to the lamp to cause the latter to glow and give a visual indication through a light emitting or observation opening 19 in the indicator casing. The indicator terminal I5 is hooked to slidably and pivotally engage a keeper slot 20 in the upper portion of the bracket l'i', adapting the indicator to be svung downward and upward into and out of operative position and to be engaged at one end with or disengaged from the bracket [1, while the indicator terminal H is provided with a locking collar or stud and a threaded stem to engage a keyhole-shaped locking slot 2| in the upper end of the bracket l8, whereby the indicator is adapted when moved into operative position to be locked to the bracket 18. In the locing and releasing actions the brackets, which are formed of spring metal, such as phosphor-bronze, are relatively spread, by bending the upper ends of either or both outwardly, to allow the stud to be engaged with or disengaged from the circular portion of the slot 2|, while the straight contracted portion of said slot is adapted to receive the threaded stem and permit the indicator end provided with the terminal IE to be moved downwardly and upwardly in an obvious manner for locking and releasing actions. The threaded stem is designed to receive a threaded knob 22 by which the indicator may be manipulated for locking and releasing movements and by which it may be clamped to the bracket or leg I 8 to hold the brackets rigidly against spreading movement.

The brackets IT and I8, as above set forth, are made of spring metal and these brackets are of similar construction with the exception of the different forms of slots 20 and 2| therein. Each bracket comprises a leg or standard 23 at the upper end of which the keeper slot 25 or 2! is formed. It has been customarily known to attach the lower ends of these legs 23 of the brackets I1 and IE to the fuse clip retaining bolts I l for not only supporting the indicator l3 above the fuse, but for locking-in the fuse to prevent its accidental withdrawal. Such leg connecting means are acceptable for new installations, but where the fuse clips are installed in an electrical circuit it is quite inconvenient and at times impossible to remove the clips without destroying the same or at least damaging their supporting connections and, therefore, my improved brackets provide means for connecting the indicators to th fuse clips without removing the latter or providing any additional connecting elements whereby the fuse will be securely locked in its fuse clips and cannot be withdrawn until the indicator is removed.

To each leg 23 I form therewith an enlarged base portion extending at right angles to one side thereof and having formed therein a rectangular opening through which may extend the jaws B of the fuse clips. The side bars or jaws 24 of the base portion of each bracket each seat themselves within one of the undercut or inwardly offset portions 1 of the fuse clips, and by rigidly connecting the opposed ends of the jaws 24 together the jaws ii of the fuse clips are prevented from being further spread apart. As the distance between the bowed portions of the jaws 6 is greater than the width of the opening within the base portion of the bracket the latter can only be inserted upon or removed from a fuse clip by first forcing the jaws of the clips together in the manner as i illustrated in Fig. 10 of the drawing or until the distance between the jaws 8 is less than that of the width of the opening within the bracket. After brackets are placed upon the fuse clips the fuse is then inserted therein and by doing so the jaws 6 are spread outwardly and forced into gripping engagement with the jaws 24 of the brackets whereat the latter are retained against longitudinal movement and further held against removal from the fuse clips. By connecting the indicator II! to these brackets the fuse is securely locked in its retaining clips and cannot be accidentally removed therefrom. These jaws 24 may be offset as shown so as to fit snugly about the bowed portions 6 of the clips or they may be made from resilient material so as to permit the same to slightly spread apart to some extent to be slipped down over the jaws 6 of the clip to a position in alinement with the instruck portions 1 and then by spring reaction to snap into engagement with these instruck portions to interlock the bracket with the clip. The jaws 24 are inclined downwardly and inwardly at an angle to the vertical plane of the bracket so that they will fit snugly in the portions 1 and lie in broad contact with and under the lower ends of the jaws 6 so as to be held by the latter and by their spring gripping action against upward displacement as well as against rocking or other body movements in any direction. When so applied the bracket will draw the clip jaws into tight engagement with the coacting fuse contact so as to prevent the objections before stated which occur when a clip does not engage a fuse contact with sufficient tightness. Also, as will be seen by reference to Figure 6, the jaws 24 normally incline from their fix-ed ends toward their free ends convergently at an alpha angle, so that when said jaws 24 are in gripping engagement with the jaws 6 they will be placed under stress to effect a tight gripping engagement between the same and the jaws 6. To strengthen the jaws 24 and to limit their spreading movement, as well as to assist in maintaining them under stress when gripped with the jaws 6, a resilient bridge piece 25 is provided. This bridge piece connects the free ends of the jaws 2'4 and is normally bowed or curved to exert a spring resistance to a spreading movement ofthe jaws, under which it is more or less fiat tened out, and to thereby supplement the stress condition and increase the binding action of the jaws 24 on the jaws E.

A pair of brackets I"! and i3 so constructed may be applied to the clips of a mounted fuse to support an indicator of the type described, and this may be easily and conveniently effected without disturbing the fuse or the fastening bolts. When so applied the brackets and glow lamp within the indicator will be electrically connected with the fuse and circuit terminals ready for an indicating action when the fuse is blown. By thus utilizing the clips as supports for th brackets all difficulties in mounting an indicator for use in connection with an already installed fuse mounting are avoided and overcome in a simple and effective manner. At the same time the brackets when applied operate as clip tightening devices to clamp the clips in close contact with the fuse terminals to avoid and overcome the stated difficulties encountered when the clips fail to engage the fuse terminals with sufficient tightness. If it should be desired at any time to remove a blown fuse and replace it with a new fuse, this may be done by first removing the indicator and forcing the brackets upward out of engagement with the clips, after which the blown fuse may be removed, a new fuse inserted, and the brackets and indicator reapplied for use.

In Figures ll and 12 I have shown a modified construction of bracket in which the jaws 24 have projecting upwardly therefrom arms 28 carrying supplemental jaws 2'1 to engage under the outturned upper ends 8 of the jaws 5 so as to hold said ends 8 of the jaws "5 from spreading and the fuse from jumping upward or from possibly being forced laterally out of the clips when the fuse mount is subjected to very violent shocks, jars or vibrations such as might cause bending or disruption of the clip jaws if not so sustained and reinforced. Brackets of this type may be used with advantage under conditions where the fuse mount is constantly or may at times be subjected to forces of a very violent character tending to cause it to jump out of its clips unless the clips are strongly braced and held in tight engagement with the fuse.

From the foregoing description, taken in connection with the drawing, the construction and mode of use of my improved indicator mounting will be readily understood, and it will be seen that it is adapted to carry out the stated objects of the invention, whereby the desirable advantages set forth are obtained, in a simple and effective manner. By the use of the improved indicator brackets an indicator may be mounted for use with an installed fuse without disturbing any of the parts of the fuse mounting, thus saving labor or avoiding trouble and expense in providing an indicator for cooperation with the installed fuse. It is to be understood that while the invention is particularly designed for the mounting of an indicator of the type specified, it is not limited thereto, as indicators of other types may be used and mounted in a similar manner. Also it is to be understood that while the use of brackets of the particular construction disclosed is preferred, the form and construction of these brackets may be varied as desired, within the scope of the appended claims, without departing from the-spirit or sacrificing any of the advantages of the invention.

Having thus described my invention, I claim:

1.- In a device of the character described, a fuse having contact terminals, clips adapted to receive the fuse and to be engaged by the fuse terminals, each clip embodying a pair of curved jaws, an electrical indicator for indicating an inoperative condition of the fuse, said indicator being provided with contact terminals, and indicator supporting brackets detachably engaged by the contact terminals of the indicator and engaging the jaws of the clips, each bracket having a pair of clip engaging spring jaws extending outwardly therefrom at a converging angle to each other and inclined convergently at an angle to the vertical plane of the bracket, and a resilient bridge piece connecting the free ends of the jaws.

2. An indicator supporting bracket for supporting a fuse blowout indicator of the character described from a fuse holding clip comprising a supporting standard having indicator supporting means at its upper end, a pair of clip engaging spring jaws at its lower end, and a bowed resilient bridge piece connecting said jaws.

3. A combined fuse indicator and lock-in device comprising clips for receiving th contact terminals of the fuse, each clip comprising a pair of bowed and spaced jaws, each jaw having an indented portion formed therein, an indicator for the fuse, supporting brackets, means for detachably connecting said indicator to one end of each bracket, a pair of jaws formed with each bracket, at the opposite ends thereof and adapted at times to be seated within indented portions of the jaws of said fuse clips, and the distance between the jaws of each bracket being less than that of the distance between the bowed portions of the jaws of the clips when the same are in their normal positions or the terminals of the fuse inserted therein whereby the brackets will be prevented from withdrawal from the clips.

4. A combined fuse indicator and lock-in device comprising clips for receiving the contact terminals of the fuse, an indicator for the fuse, brackets connected to said indicator, a base portion formed with each bracket, means for detachably connecting said base portion of each bracket to a fuse clip and a leg formed with each bracket for supporting said indicator above the fuse for preventing the accidental removal of the contact terminals thereof from said clips.

5. A bracket for fuse indicators comprising a supporting leg, a base portion extending from said leg and having an opening therein, a pair of gripping jaws formed with said base portion and arranged at the opposed sides of the opening formed therein, and means for connecting the opposite ends of said jaws together.

6. A bracket for fuse indicators stamped from a single strip of metal forming a leg portion, one end of said leg portion having a slot formed therein whereby an indicator may be connected thereto, a base portion formed with the opposite end of said leg portion and extending at right angles thereto, a pair of spaced jaws formed with said base portion and means for connecting the opposite ends of said jaws together.

'7. A combined fuse indicator and lock-in device comprising a pair of substantially U-shaped retaining clips, the opposed legs of each clip beof the legs of said retaining clips, an indicator casing, and means for removably connecting said indicator casing to said supporting legs whereby said casing may at times be retained between said clips and arranged above the fuse retained therein.

WILLIAM C. LIN'I'ON. 

